1. Field of the Invention
This invention relates generally to thermal transfer printing, and more particularly is directed to an improved method for forming an image on a printing paper by the selective transfer thereto of disperse dye from a dye carrier in response to the selective application of thermal energy to the carrier while in contact with the printing paper, and also to an improved printing paper for receiving the disperse dye.
2. Description of the Prior Art
As a rule, thermal transfer printing employs a printing paper formed of cellulose fibers to which a disperse dye is selectively transferred from a dye carrier in the form of an ink ribbon or web. It is well known that disperse dye efficiently colors the printing paper when the dye is in a mono-molecular state as a result of the diffusing of the disperse dye between molecules of the printing paper. However, the distance between cellulose molecules is smaller than the dimensions of the disperse dye molecules so that it is very difficult for the disperse dye to diffuse into the usual printing paper formed of cellulose fibers. Accordingly, some of the disperse dye transferred from the carrier to the printing paper remains in a crystalline state on the surfaces of the cellulose fibers forming the printing paper, and thus cannot be in the mono-molecular state necessary for clearly generating the respective color as is required for producing a clear color image. Further, if the surface of the printing paper to which the disperse dye is selectively transferred from a dye carrier is non-porous and very smooth, the ink ribbon or web constituting the dye carrier and the printing paper frequently stick to each other.